Carl mentioned that he saw some nasty performance issues with threads
that had a lot of HTML messages in them.

If you are experiencing this problem, would you mind trying some
alternative mm-text-html-renderer setting:

http://mh-e.sourceforge.net/manual/html/HTML.html

Also, if you have elinks, I recommend my custom renderer:

(require 'mm-view)
(add-to-list 'mm-text-html-renderer-alist 
  '(elinks mm-inline-render-with-stdin nil "elinks" "-force-html" "-dump"))
(setq mm-text-html-renderer 'elinks)


Alex